diff options
| author | Alexander Gordeev | 2021-11-04 07:14:46 +0100 |
|---|---|---|
| committer | Heiko Carstens | 2021-12-16 19:58:08 +0100 |
| commit | 4c88bb96e40b757f4796f70a4a7507df554467c4 (patch) | |
| tree | c67090799526e8f853c3790a69b4e54e2ed8906f /arch/s390 | |
| parent | 1194372db6f3c917c9c6f6907e8378cf1076c557 (diff) | |
s390/mm: check 2KB-fragment page on release
When CONFIG_DEBUG_VM is defined check that pending remove
and tracking nibbles (bits 31-24 of the page refcount) are
cleared. Should the earlier stages of the page lifespan
have a race or logical error, such check could help in
exposing the issue.
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Diffstat (limited to 'arch/s390')
| -rw-r--r-- | arch/s390/mm/pgalloc.c | 41 |
1 files changed, 30 insertions, 11 deletions
diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c index 5d5549843c5c..fd35c1a0213b 100644 --- a/arch/s390/mm/pgalloc.c +++ b/arch/s390/mm/pgalloc.c @@ -311,10 +311,23 @@ unsigned long *page_table_alloc(struct mm_struct *mm) return table; } +static void page_table_release_check(struct page *page, void *table, + unsigned int half, unsigned int mask) +{ + char msg[128]; + + if (!IS_ENABLED(CONFIG_DEBUG_VM) || !mask) + return; + snprintf(msg, sizeof(msg), + "Invalid pgtable %p release half 0x%02x mask 0x%02x", + table, half, mask); + dump_page(page, msg); +} + void page_table_free(struct mm_struct *mm, unsigned long *table) { + unsigned int mask, bit, half; struct page *page; - unsigned int bit, mask; page = virt_to_page(table); if (!mm_alloc_pgste(mm)) { @@ -337,10 +350,14 @@ void page_table_free(struct mm_struct *mm, unsigned long *table) mask >>= 24; if (mask != 0x00U) return; + half = 0x01U << bit; } else { - atomic_xor_bits(&page->_refcount, 0x03U << 24); + half = 0x03U; + mask = atomic_xor_bits(&page->_refcount, 0x03U << 24); + mask >>= 24; } + page_table_release_check(page, table, half, mask); pgtable_pte_page_dtor(page); __free_page(page); } @@ -380,28 +397,30 @@ void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table, void __tlb_remove_table(void *_table) { - unsigned int mask = (unsigned long) _table & 0x03U; + unsigned int mask = (unsigned long) _table & 0x03U, half = mask; void *table = (void *)((unsigned long) _table ^ mask); struct page *page = virt_to_page(table); - switch (mask) { + switch (half) { case 0x00U: /* pmd, pud, or p4d */ free_pages((unsigned long) table, 2); - break; + return; case 0x01U: /* lower 2K of a 4K page table */ case 0x02U: /* higher 2K of a 4K page table */ mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24)); mask >>= 24; if (mask != 0x00U) - break; - fallthrough; + return; + break; case 0x03U: /* 4K page table with pgstes */ - if (mask & 0x03U) - atomic_xor_bits(&page->_refcount, 0x03U << 24); - pgtable_pte_page_dtor(page); - __free_page(page); + mask = atomic_xor_bits(&page->_refcount, 0x03U << 24); + mask >>= 24; break; } + + page_table_release_check(page, table, half, mask); + pgtable_pte_page_dtor(page); + __free_page(page); } /* |